1. Field of the Invention
The present invention relates to a differential amplifier circuit and a semiconductor integrated circuit device, and more particular, to a differential amplifier circuit mounted on a receiving circuit of a signal transmission system.
2. Description of the Related Art
Recently, the performance of components used in computers and other information processing apparatuses has been greatly improved. In particular, dramatic improvements have been made, for example, in the performance of processors and semiconductor memory devices such as SRAMs (Static Random Access Memories) and DRAMs (Dynamic Random Access Memories). The improvements in the performance of semiconductor memory devices, processors, and the like have come to the point where system performance cannot be improved further unless the speed of signal transmission between components or elements is increased.
Specifically, the speed of signal transmission between a main memory device such as a DRAM and a processor (i.e., between LSIs), for example, is becoming a bottleneck impeding performance improvement for a computer as a whole. Furthermore, the need for the improvement of signal transmission speed is increasing not only for signal transmission between cabinets or boards (printed wiring boards), such as between a server and a main memory device or between servers connected via a network, but also for signal transmission between chips or between devices or circuit blocks within a chip because of increasing integration and increasing size of semiconductor chips, decreasing supply voltage levels (low-voltage-swing signals), etc.
The signal is transmitted at high speed often with a small amplitude to prevent the loss of the high frequency component or the signal reflection. For this reason, the receiving circuit is required to include a signal amplifier circuit capable of amplifying the signal of small amplitude accurately, and a signal amplifier circuit (differential amplifier circuit) meeting this requirement has been in demand.
The prior art and the problems associated with the prior art will be described in detail later with reference to accompanying drawings.